In the conventional manufacture of sealed insulated units comprising an assembly of two spaced apart parallel sheets of substrate (usually glass) and a bondable and/or curable spacer therebetween, assembled units are positioned in a press and the entire unit is heated to melt and/or cure the spacer allowing the spacer to bond to the substrates. Heating of the entire unit causes problems since it increases the temperature of the entire unit including the air between the substrates. In addition, if the entire unit is being heated in the vertical position, a "chimney" effect occurs whereby the upper zone of the unit may become overheated relative to the lower zone with problems resulting.
For example, in U.S. Pat. No. 5,567,258, an IG unit containing an aluminum spacer, aluminum tape corner keys and a thermoset resin sealant is placed within a tunnel having microwave generators on each side. The unit passes through the tunnel and the entire IG unit is subjected to microwave energy to bond the spacer to the substrates. Conventional presses ensure that the spacer is firmly bonded to the substrates. The entire spacer however, is heated which can result in softening of the spacer and changes in the shape of the spacer.
U.S. Pat. No. 4,683,154 discloses a window panel held in a spaced apart manner by glass beads and sealed by welded glass obtained by welding the bead spacers together with a laser beam while positioned in a vacuum furnace. The laser welding occurs while the IG unit is in the furnace and is directed around the perimeter of the IG unit by a combination of rotating the IG unit and aiming the laser with mirrors.
Drawbacks of the conventional art include higher energy consumption, higher heat dissipation requirement, increased fabrication time and overheating of the IG assembly and spacer. It is an object of the present invention to overcome the disadvantages of the prior art by using localized zonal heating or other energy source to heat or otherwise induce an effect (e.g. for curing) within the spacer of the IG assembly in the zone(s) of the assembly where the spacer is positioned between the substrates.